Anechoic chamber system

ABSTRACT

A system for attaching anechoic wedge elements to the walls of an anechoic chamber. One or more struts are affixed to the chamber wall to hold nuts. Support rods are screwed into the nuts and partially covered with a mat of batting. Wedge elements are affixed to support tubes with spring-receiving slots therein. The tubes slide over the rods and are held by the springs, allowing easy installation of the wedge elements.

United States Patent 91 [111 3,735,837 Duda et al. 1 May 29, 1973 [54] ANECHOIC CHAMBER SYSTEM 2,655,348 10/1953 Siering ..l8l/30 X 3,604,5 1 91971 H ..l8l 33 [75] Inventors: John Duds, Durnont, N.J.; Stan 3 l m I GD f f R'verdage; Ame Kaumm" Primary Examiner-Richard B. Wilkinson Plalnview, both 0 NY. 4gigmigqm n qhn F Gonzales v [73] Assignee: Industrial Acoustics Company, n y-George B. Finnegan, Jr., Granville M.

Bronx, NY. Pine, Thomas R. MacDonald et al.

[2]] App! 244896 A system for attaching anechoic wedge elements to the walls of an anechoic chamber. One or more struts s2 U.S. Cl ..181/33 GE are affixed to the chamber wall to hold nutspp [51] Int. Cl. ..E04b 1/82 rods are s d nt th nuts and partially covered [58] Field of Search ..181/33 GE, 33 GD, h a mat Of ng- W ge elements are affixed to l8l/33 GB, 33 E, 30; 340/5 A; 343/18 A support tubes with spring-receiving slots therein. The tubes slide over the rods and are held by the springs, [56] Referencgs Cit d allowing easy installation of the wedge elements.

UNITED STATES PATENTS 11 Claims, 6 Drawing Figures 2,160,638 5/1939 Bedell etal. ..181/33 G'D'Ux PATENIEB MAY 2 9 I973 SHEET 1 or 3 PATENTEDHAYZS I975 SHEET 2 or 3 F IG. 5 8/ PATENTH] MAY 2 9 I975 sum 3 or 3 ANECI-IOIC CHAMBER SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a system for easily installing anechoic wedge elements on the walls of an anechoic chamber.

2. Description of the Prior Art Acoustic chambers have been designed in which the walls are covered with wedge-like elements which serve to eliminatesubstantially all of the echoes in a given frequency range from the chamber wall. While the preferred anechoic wedge for most purposes is a true mathematical wedge, nevertheless other shapes, such as pyramids, cones, hyperbolic surfaces of rotation, hemispheres, etc., are used and are included within the scope of the term anechoic wedge. These wedges are constructed of a material which absorbs most of the energy of incident sound waves.

Assembly of the anechoic wedges to cover the wall of an anechoic chamber requires some type of support for the wedges. This support is typically provided by providing flanges on a wedge or integral group of wedges and by providing slots in a support system to engage the flanges. These prior art systems are frequently difficult to install. It is quite difficult to remove the wedges and realign or replace them with differently tuned or aligned wedges.

SUMMARY OF THE INVENTION The invention provides an improved system for mounting wedges firmly while in use, while permitting easy removal or replacement. In essence the invention includes an interacting rod and tube, one carried by the supporting structureand the other included as part of the anechoic wedge, such that the rod slips inside the tube and is firmly engaged by the tube when the wedge is in its desired position.

In the preferred embodiment, atube is partially inserted along the axis of a stiff foam wedge and glued into place, for engagement with a supporting rod. A pair of slots in the protruding part ofthe tube are fitted with a resilient clip so that as the tube slides over the rod, the clip opens by reacting against a slot wall having a positive rake angle and allowing easy insertion of the rod in the tube. The spring closes when movement stops, holding the tube fairly firmly in place on the rod. Sliding removal is possible, but more force is required because the spring bears on a slot wall having a negative rake angle.

If desired, the rod can be threaded or otherwise provided with a roughened surface for improved frictional holding by the clip, and can be fixed to the wall in any manner. In the preferred embodiment, however, a special strut is provided to hold nuts into which the threaded rod is screwed. It is preferable to place a mat of acoustic batting against the wall over the strut before the wedge is attached.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overallexploded view of a wedge installation system according to the present invention.

FIG. 2 is a detailed view of the exposed tip of rod 12 in FIG.'1.

FIG. 3 is a perspective view of the spring 14 of FIG. I.

FIG. 4 is a detailed view showing the spring 14 installed in the tip of rod 12.

FIG. 5 is a partial cut-away view of two wedges installed according to the present invention.

FIG. 6 is a perspective view of several wedges installed on a chamber wall.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is an exploded overall view of the system for attachment of one anechoic wedge to the chamber wall. A strut 2 is provided with a plurality of nuts such as nut 4 within a recessed area of the strut. A cylindrical support rod 6 is screwed into nut 4 and is covered by a mat of acoustical batting 8. The mat is pierced by the support rod and fits snugly against the strut and the chamber wall. An anechoic wedge 10, preferably constructed of rigid, open cell, foam polyurethane, is pierced by and glued onto a support tube 12. A spring 14 is fitted into slots 16 and 18 in the walls of the support tube. The wedge is then attached to the chamber wall by sliding the support tube over the support rod and allowing the spring 14 to hold the tube firmly in place over the rod once inserted.

The strut 2 includes a rectangular back wall 16 having two elongated edges 18 and 20 and two short edges 22 and 24. The back wall is adapted to be fixed to a chamber wall by being mounted flush against it in a plane parallel to and adjacent to the chamber wall. There are two symmetrical outwardly extending walls, only one of which will be described here in detail. A rectangular outwardly extending wall 26 includes first and second elongated edges 28 and 30 and two short edges-32 and 34. The first elongated edge 28 or the outwardly extending wall 26 is integrally attached to the elongated edge 18 of the back wall. This integral attachment may be made by welding or brazing separate wall sections together or by constructing the several walls by bending a single sheet of planar material.

First and second coplanar walls 36 and 38 are provided, of which only wall 36 will be described in detail. Rectangular coplanar wall36 is in the same plane with wall 38 and has elongated edges 40 and 42 and short edges 44 and 46'. The first "elongated edge 40 of coplanar wall 36 is integrally attached to the second elongated edge 30 of outwardly directed wall 26. The coplanar walls 36 and 38 are separated by a gap 48, behind which female screw threads 50 of nut 4 are situated.

There are first and second inwardly directed walls 52 and 54,of which only the second inwardly directed wall 54 is easily visible in FIG. 1. Wall 54 has first and second elongated edges 56 and 58 and two short edges 60 and 62. The first elongated edge 56 of inwardly directed wall 54 is integrally attached to a second elongated edge 64 of coplanar wall 38. The second elongated edges of inwardly directed walls 52 and 54 stop short of the back wall to leave two gaps 66 and 68, into which flanges (not illustrated in FIG. 1) of nut 4 can be inserted.

The cylindrical support rod 6 has a male screw thread 70 on one end thereof, by which the support rod is screwed into the female screw thread of nut 4. The male screw thread 70 is of sufficient length to leave some thread exposed when the support rod is fully screwed into the corresponding nut. The support rod 6 pierces the mat batting 8 by means of a hole 72 through the mat. This batting is usually sufficiently light that there is no need to prepare the hole 72 in advance, it being sufficient to create the hole by forcing the mat batting over the support rod.

The wedge 10 is shown glued to the support tube 12 including slots 16' and 18. These slots are shown more clearly in FIG. 2. Slots 16 and 18 are symmetrically arranged with respect to the support tube. While it would be possible to operate the system by providing only one slot rather than two slots, two slots are used in the preferred embodiment. The inside diameter of the support tube is such that it will slide over and fit closely to the support rod 6. The end of the tube closest to the slot is slidable over the support rod 6. Each slot has first and second walls. As illustrated in connection with slot 16', there is a slot 74 with a negative rake angle on the end of the support tube nearest the strut, and there is a slot 76 with a positive rake angle on the end of the tube closest to the anechoic wedge.

FIG. 3 is a perspective view of the spring 14 illustrated in FIG. 1. The spring has two longer sections 78 and 80, arranged approximately in parallel with each other, to be respectively fitted into slots 16 and 18 of the support tube. A first end 82 of longer spring section 80 provides one end of the lock spring 14. A shorter spring section 84 has a first end 86 which is integrally connected to a first end 88 of spring section 78. The second end 90 of the shorter spring section provides the other end of lock spring 14. Connected between second ends 92 and 94 respectively of longer sections 78 and 80 is a bent spring section 96 in the shape of a capital letter omega and having ends 98 and 100 respectively connected to the second ends 92 and 94 of the longer spring sections. The bent spring section is situated in a plane substantially perpendicular to the plane of the two longer spring sections.

FIG. 4 is a view showing the attachment of the lock spring 14 into the slots 16 and 18 of tube 12. The lock spring is snapped into the two slots as illustrated in this figure. It will be seen that, as the tube is forced over the support rod, the positive rake of the slot walls forces the two longer spring sections of spring 14 to separate, allowing the tube to be relatively easily forced onto the rod down to the end where the spring sections can grip the exposed male thread of the support rod. The negative rake angle on the other side of the slot forces the longer spring segments together when it is attempted to pull the tube off the rod, thereby making removal of the tube from the rod more difficult than the installation thereof.

FIG. is a partial cut-away view of first and second anechoic wedges l0 and affixed to a chamber wall 102 by a support system as described in connection with FIG. 1. As can be seen from a combination of FIG. 1 and FIG. 5, the preferred embodiment of the anechoic wedge has six sides, including a substantially square base 104, two parallel slightly truncated triangular sides 106 and 108, two substantially rectangular sides 110 and 112, and a small elongated peak plane 114. The triangular sides each have a base edge, two slant edges, and a short truncated peak edge, the square base has two sets of two substantially equal opposite edges, the two rectangular sides each have two long edges and two short edges, and the small elongated peak plane has two long edges and two short edges. Although the preferred embodiment has the truncated peak plane, it is possible to produce the wedges with two perfect triangular sides, in which case the wedges will be five sided rather than six sided. It is also possible to produce the wedges as cones, pyramids, and other appropriate shapes for anechoic effect.

However, in the preferred embodiment, the base edges of the truncated triangular sides are attached to opposite edges of the square side, one short edge of each rectangular side is attached to the other opposite edges of the square base, the slant edges of the truncated triangular sides are attached to the associated elongated edges of the rectangular sides, and one short edge of each rectangular side and the truncated peak edge of the triangular sides adjoin the respective sides of the truncated peak plane. .It should be noted that this is a description of the outside surface of a preferably integrally constructed solid body of open-cell foamed polyurethane, and the description of the sides does not imply that they produce a hollow wedge.

FIG. 6 is a perspective view of a group of wedges attached to a chamber wall. This figure illustrates the selectively variable attachment of the wedges in different orientations. It is apparent that the invention makes possible individual positioning of wedges 10 without disassembly of the entire multi-wedge unit, as in prior systems. Thus, each separate wedge can be positioned, turned or removed independently of the others even though it may be located in the middle of an array of wedges.

Although the preferred embodiment utilizes a spring clip (14) to engage the threads of a supporting rod, certain other forms may be acceptable: for example, a sharp-edged spring clip could be used wherein the sharp edge engages the the rod so as to cut into the rod surface slightly if a force is exerted tending to pull the wedge away from its support. In such case the slot 16' may assume a different shape, e.g., a lessened rake angle, particularly if the sharp-edged slip is formed like a conical open washer.

It is also evident that the relative positions of the rod and tube can be interchanged without vitally affecting their respective functions. In this case, of course, the tube must be suitably threaded or otherwise formed for support by the strut.

We claim:

1. A system for installing anechoic wedges to a chamber wall comprising: p

A. a rod affixable to the chamber wallto extend outwardly therefrom B. an anechoic wedge constructed of a body of material which absorbs most of the energy of incident sound waves and having a base section,

C. a tube fixedly inserted through the base section and into the body of the anechoic wedge, the tube including a tube portion protruding from the base section of the wedge material and provided with a slot in said portion, the tube being slidable over the rod, and

D. spring clamp means fitted onto the tube through the slot for clamping against the rod to thereby hold the tube in place on the rod.

2. A system according to claim 1 further comprising:

A. a strut affixed to the chamber wall and having a recess therein, and

B. a nut arranged to be held in the recess and having a female screw thread therein, the rod having a male screw thread thereon engaged by the female screw thread, therebyaffixing the rod firmly to the chamber wall.

3. A system according to claim 2 wherein the recess in the strut is formed by gaps between a back wall and inwardly directed walls of the strut, and wherein flanges of the nut are situated within the gaps and firmly held in place by pressure from the engaging wall.

4. In a system for installing anechoic wedges to rods affixed to a chamber wall and extending outwardly therefrom, the improved anechoic wedge support system comprising:

A. an anechoic wedge constructed of a body of sound-absorbent material and having a base section,

B. a tube fixedly inserted through the base section and into the body of the anechoic wedge, the tube including a tube portion protruding from the base section of the wedge and provided with a slot in said portion, the tube having an internal diameter slightly greater than the external diameter of the rods, and

C. spring clamp means fitted onto the tube through the slot for clamping against the rod to thereby hold the tube in place when inserted onto the rod.

5. The improved wedge support system of claim 4 wherein the base section of the anechoic wedge is substantially square, thereby allowing a plurality of anechoic wedges to be mounted contiguously on a chamber wall with the orientation of each base section being selectable from two mutually perpendicular orientations.

6. The improved wedge support system of claim 4 wherein the tube portion protruding from the base section of the wedge is provided with two slots in symmetrically opposite walls of the tube, each slot having a first wall nearest to the base section of the wedge and a second wall farthest from the base section of the wedge, the first wall having a positive rake angle and the second wall having a negative rake angle.

7. The improved wedge support system of claim 6 wherein the spring clamp means comprises two longer spring sections fitting respectively in the two slots, a shorter spring section for holding the spring clamp in place on the tube, and a bent spring section to allow the spring clamp to open partially when the longer spring sections ride up on the respective slot walls having the positive rake angles.

8. The improved wedge support system of claim 7 wherein the base section of the anechoic wedge is substantially square, thereby allowing a plurality of anechoic wedges to be mounted contiguously on a chamber wall with the orientation of each base section being selectable from two mutually perpendicular orientations.

9. An anechoic chamber system comprising:

A. a strut comprising:

A1. a back wall having first and second elongated edges and two short edges, the back wall being adapted to be fixed to a chamber wall in a plane parallel to and adjacent to the chamber wall,

A2. first and second outwardly extending walls each having first and second elongated edges and two short edges, the first elongated edge of each of the perpendicular walls being integrally attached to a respective one of the elongated edges of the back wall, whereby the first and second outwardly extending walls respectively extend outwardly from opposite elongated edges of the back wall, thereby being adapted to extend outwardly from the chamber wall,

A3. first and second coplanar walls each having first and second elongated edges and having two short edges which are respectively less than half the length of either of the two short edges of the back wall, the first elongated edge of each of the coplanar walls being respectively integrally attached to the second elongated edge of one of the outwardly directed walls, whereby the first and second coplanar walls are in the same plane and are separated by a first gap, thereby being adapted to be placed in a plane parallel to and separated from the chamber wall, and

A4. first and second inwardly directed walls each having first and second elongated sides and having two short edges which are respectively shorter than the two short edges of the outwardly directed walls, the first elongated edge of each of the inwardly directed walls being respectively integrally attached to the second elongated edge of one of the coplanar walls, whereby the first and second inwardly directed walls are inwardly directed toward the back wall with the second elongated edge of each of the inwardly directed walls being respectively separated from the back wall by second and third substantially equal gaps, thereby being adapted to be inwardly directed toward the chamber wall,

B. first and second nuts, each comprising first and second flanges and a female screw thread, the first and second flanges being respectively fitted in the second and third gaps, the female screw thread being situated behind the first gap,

C. first and second cylindrical support rods, each having a male screw thread on one end thereof and being screwed into the female screw thread on a corresponding one of said first and second nuts, the male screw thread being of sufficient length to leave some thread exposed when the support rod is fully screwed into the corresponding nut,

D. a mat of acoustical batting placed over the strut and pierced by the supporting rods, the mat being adapted to be situated adjacent to the strut and to portions of the chamber wall not covered by a strut,

E. first and second cylindrical support tubes respectively slidably fitted closely over the first and second support rods, each tube having a first end situated close to the strut and a second end situated remote from the strut, each of the tubes having first and second symmetrical slots cut in opposite cylindrical walls thereof near the first end thereof, each slot having first and second walls, the first wall being situated toward the first end of the tube and being slanted to provide a negative rake angle, the second wall being situated toward the second end of the tube and being slanted to provide a positive rake angle, the slots being situated over the exposed thread of the support rod,

F. first and second lock springs respectively fitted into the slots of the first and second support tubes and gripping the exposed threads of the support rod, each lock spring comprising:

Fl. first and second longer spring sections arranged approximately in parallel and respectively fitted into the first and second symmetrical slots of the associated support tube, each longer spring section having first and second ends, the first end of the first longer spring section providing one of two ends of the lock spring,

F2. a shorter spring section having first and second ends, the first end of the shorter section being integrally connected to the first end of the second longer spring section, the shorter spring section being in the plane of the two longer spring sections and substantially perpendicular thereto, the second end of the shorter spring section providing the other of the two ends of the lock spring, and

F3. a bent spring section in the shape of a capital letter omega and having first and second ends re spectively integrally attached to the second ends of the first and second longer sections, the bent spring section being situated in a plane substantially perpendicular to said plane of the two longer spring sections,

G. a first anechoic wedge constructed of rigid, opencell, foamed polyurethane and formed with a substantially square base, two parallel slightly truncated triangular sides each having a base edge, two sland edges and a short truncated peak edge, the base edges respectively adjoining two opposite edges of the square base, two substantially rectangular sides each having two long edges and first and second short edges, the first short edge of each rectangular side adjoining a respective one of the other two opposite edges of the square base, the two long edges of each rectangular side adjoining adjacent slant edges of the triangular side, a small elongated peak plane having two long edges and two short edges, the two long edges of the peak plane being respectively adjacent to the second short edge of the rectangular sides, the two short edges of the peak plane being respectively adjacent to the two truncated peak edges of the triangular planes, the first support tube being inserted perpendicularly through the center of the square base and piercing deeply into the first anechoic wedge, the first support tube being fixed by glue to the interior of the wedge, two of the edges of the square base being arranged in parallel to the elongated edges of the back wall of the strut, and

H. a second similarly constructed anechoic wedge pierced through the center of its square side and into the wedged by the second support tube, affixed thereto by glue, long edges of a peak plane of the second wedge being situated perpendicularly to the long edges of the peak plane of the first wedge.

10. An anechoic wedge assembly, comprising:

A. an anechoic wedge capable of attenuating incident sound waves reflected therefrom,

B. an elongated member extruding from a mounting portion of the wedge,

C. a support member adapted for mounting to a support structure, one of said members being dimensioned to receive slidably the other member at the interior thereof,

D. a resilient clamp carried by the receiving member and openable to engage the other member so as to permit relative motion of the two members in a direction tending to mate the members and so as to resist relative motion of the two members in the opposite direction.

11. The anechoic assembly of claim 10, wherein:

A. the receiving member includes at least one slot communicating with the interior of the member, and the resilient clamp includes a portion coacting with the slot and yieldably engages the other member when received by the receiving member. 

1. A system for installing anechoic wedges to a chamber wall comprising: A. a rod affixable to the chamber wall to extend outwardly therefrom B. an anechoic wedge constructed of a body of material which absorbs most of the energy of incident sound waves and having a base section, C. a tube fixedly inserted through the base section and into the body of the anechoic wedge, the tube including a tube portion protruding from the base section of the wedge material and provided with a slot in said portion, the tube being slidable over the rod, and D. spring clamp means fitted onto the tube through the slot for clamping against the rod to thereby hold the tube in place on the rod.
 2. A system according to claim 1 further comprising: A. a strut affixed to the chamber wall and having a recess therein, and B. a nut arranged to be held in the recess and having a female screw thread therein, the rod having a male screw thread thereon engaged by the female screw thread, thereby affixing the rod firmly to the chamber wall.
 3. A system according to claim 2 wherein the recess in the strut is formed by gaps between a back wall and inwardly directed walls of the strut, and wherein flanges of the nut are situated within the gaps and firmly held in place by pressure from the engaging wall.
 4. In a system for installing anechoic wedges to rods affixed to a chamber wall and extending outwardly therefrom, the improved anechoic wedge support system comprising: A. an anechoic wedge constructed of a body of sound-absorbent material and having a base section, B. a tube fixedly inserted through the base section and into the body of the anechoic wedge, the tube including a tube portion protruding from the base section of the wedge and provided with a slot in said portion, the tube having an internal diameter slightly greater than the external diameter of the rods, and C. spring clamp means fitted onto the tube through the slot for clamping against the rod to thereby hold the tube in place when inserted onto the rod.
 5. The improved wedge support system of claim 4 wherein the base section of the anechoic wedge is substantially square, thereby allowing a plurality of anechoic wedges to be mounted contiguously on a chamber wall with the orientation of each base section being selectable from two mutually perpendicular orientations.
 6. The improved wedge support system of claim 4 wherein the tube portion protruding from the base section of the wedge is provided with two slots in symmetrically opposite walls of the tube, each slot having a first wall nearest to the base section of the wedge and a second wall farthest from the base section of the wedgE, the first wall having a positive rake angle and the second wall having a negative rake angle.
 7. The improved wedge support system of claim 6 wherein the spring clamp means comprises two longer spring sections fitting respectively in the two slots, a shorter spring section for holding the spring clamp in place on the tube, and a bent spring section to allow the spring clamp to open partially when the longer spring sections ride up on the respective slot walls having the positive rake angles.
 8. The improved wedge support system of claim 7 wherein the base section of the anechoic wedge is substantially square, thereby allowing a plurality of anechoic wedges to be mounted contiguously on a chamber wall with the orientation of each base section being selectable from two mutually perpendicular orientations.
 9. An anechoic chamber system comprising: A. a strut comprising: A1. a back wall having first and second elongated edges and two short edges, the back wall being adapted to be fixed to a chamber wall in a plane parallel to and adjacent to the chamber wall, A2. first and second outwardly extending walls each having first and second elongated edges and two short edges, the first elongated edge of each of the perpendicular walls being integrally attached to a respective one of the elongated edges of the back wall, whereby the first and second outwardly extending walls respectively extend outwardly from opposite elongated edges of the back wall, thereby being adapted to extend outwardly from the chamber wall, A3. first and second coplanar walls each having first and second elongated edges and having two short edges which are respectively less than half the length of either of the two short edges of the back wall, the first elongated edge of each of the coplanar walls being respectively integrally attached to the second elongated edge of one of the outwardly directed walls, whereby the first and second coplanar walls are in the same plane and are separated by a first gap, thereby being adapted to be placed in a plane parallel to and separated from the chamber wall, and A4. first and second inwardly directed walls each having first and second elongated sides and having two short edges which are respectively shorter than the two short edges of the outwardly directed walls, the first elongated edge of each of the inwardly directed walls being respectively integrally attached to the second elongated edge of one of the coplanar walls, whereby the first and second inwardly directed walls are inwardly directed toward the back wall with the second elongated edge of each of the inwardly directed walls being respectively separated from the back wall by second and third substantially equal gaps, thereby being adapted to be inwardly directed toward the chamber wall, B. first and second nuts, each comprising first and second flanges and a female screw thread, the first and second flanges being respectively fitted in the second and third gaps, the female screw thread being situated behind the first gap, C. first and second cylindrical support rods, each having a male screw thread on one end thereof and being screwed into the female screw thread on a corresponding one of said first and second nuts, the male screw thread being of sufficient length to leave some thread exposed when the support rod is fully screwed into the corresponding nut, D. a mat of acoustical batting placed over the strut and pierced by the supporting rods, the mat being adapted to be situated adjacent to the strut and to portions of the chamber wall not covered by a strut, E. first and second cylindrical support tubes respectively slidably fitted closely over the first and second support rods, each tube having a first end situated close to the strut and a second end situated remote from the strut, each of the tubes having first and second symmetrical slots cut in opposite cylindrical walls thereof near the first end therEof, each slot having first and second walls, the first wall being situated toward the first end of the tube and being slanted to provide a negative rake angle, the second wall being situated toward the second end of the tube and being slanted to provide a positive rake angle, the slots being situated over the exposed thread of the support rod, F. first and second lock springs respectively fitted into the slots of the first and second support tubes and gripping the exposed threads of the support rod, each lock spring comprising: F1. first and second longer spring sections arranged approximately in parallel and respectively fitted into the first and second symmetrical slots of the associated support tube, each longer spring section having first and second ends, the first end of the first longer spring section providing one of two ends of the lock spring, F2. a shorter spring section having first and second ends, the first end of the shorter section being integrally connected to the first end of the second longer spring section, the shorter spring section being in the plane of the two longer spring sections and substantially perpendicular thereto, the second end of the shorter spring section providing the other of the two ends of the lock spring, and F3. a bent spring section in the shape of a capital letter omega and having first and second ends respectively integrally attached to the second ends of the first and second longer sections, the bent spring section being situated in a plane substantially perpendicular to said plane of the two longer spring sections, G. a first anechoic wedge constructed of rigid, open-cell, foamed polyurethane and formed with a substantially square base, two parallel slightly truncated triangular sides each having a base edge, two sland edges and a short truncated peak edge, the base edges respectively adjoining two opposite edges of the square base, two substantially rectangular sides each having two long edges and first and second short edges, the first short edge of each rectangular side adjoining a respective one of the other two opposite edges of the square base, the two long edges of each rectangular side adjoining adjacent slant edges of the triangular side, a small elongated peak plane having two long edges and two short edges, the two long edges of the peak plane being respectively adjacent to the second short edge of the rectangular sides, the two short edges of the peak plane being respectively adjacent to the two truncated peak edges of the triangular planes, the first support tube being inserted perpendicularly through the center of the square base and piercing deeply into the first anechoic wedge, the first support tube being fixed by glue to the interior of the wedge, two of the edges of the square base being arranged in parallel to the elongated edges of the back wall of the strut, and H. a second similarly constructed anechoic wedge pierced through the center of its square side and into the wedged by the second support tube, affixed thereto by glue, long edges of a peak plane of the second wedge being situated perpendicularly to the long edges of the peak plane of the first wedge.
 10. An anechoic wedge assembly, comprising: A. an anechoic wedge capable of attenuating incident sound waves reflected therefrom, B. an elongated member extruding from a mounting portion of the wedge, C. a support member adapted for mounting to a support structure, one of said members being dimensioned to receive slidably the other member at the interior thereof, D. a resilient clamp carried by the receiving member and openable to engage the other member so as to permit relative motion of the two members in a direction tending to mate the members and so as to resist relative motion of the two members in the opposite direction.
 11. The anechoic assembly of claim 10, wherein: A. the receiving member includes at least one slot communicating with the interior of the member, and the resilient clamp includes a portion coacting with the slot and yieldably engages the other member when received by the receiving member. 